1. Field of the Invention
The present invention relates to a power transmission apparatus for a vehicle having a gear transmission capable of transmitting power from a crankshaft of an engine to driving wheels by selectively establishing a plurality of stages of gear trains and a clutch for cutting power transmission from the crankshaft to the gear transmission when shifting the gear transmission. In particular, the present invention relates to an improvement in a power transmission apparatus for shifting a gear transmission by an actuator such as an electric motor.
2. Description of Background Art
There has already been known a power transmission apparatus for shifting a gear transmission by an actuator such as a motor in, for example, Japanese Patent Laid-Open No. H11-82734.
According to the construction of the above-identified reference, in order to facilitate speed shift operation of a vehicle driver such that a clutch is automatically cut in cooperation with shifting of a gear transmission, a shift change mechanism provided to the gear transmission and a clutch are mechanically connected by a link mechanism or the like.
However, when the shift change mechanism and the clutch are mechanically cooperated by the link mechanism or the like, by an increase in clutch load accompanied by an increase in displacement of an engine mounted to a vehicle, an increase in weight caused by an increased in rigidity of the link mechanism or the like may result or a deterioration in shift operability accompanied by an increase in shift load or shift operation stroke in the shift change mechanism may result.
The present invention has been carried out in view of such a situation and it is an object thereof to provide a power transmission apparatus for a vehicle which promotes shifting while avoiding an increase in weight when operating to engage or disengage a clutch in cooperation with shifting of a gear transmission.
In order to achieve the above-described object, a first aspect of the present invention includes a power transmission apparatus for a vehicle having a gear transmission capable of transmitting power from a crankshaft of an engine to driving wheels by selectively establishing a plurality of shift stages of gear trains and a clutch for cutting power transmission from the crankshaft to the gear transmission when shifting the gear transmission, the power transmission apparatus including a first actuator for shifting the gear transmission and a second actuator for driving the clutch independently of the first actuator.
According to such a construction, the gear transmission and the clutch are not mechanically connected. Accordingly, even when clutch load is increased in accordance with an increase in displacement of an engine, it is not necessary to increase the rigidity of a link mechanism or the like and an increase in weight can be avoided. Furthermore, the clutch load does not influence the shift load or shift operation stroke and accordingly, the shift operability can be promoted.
Furthermore, a second aspect of the present invention includes, in addition to the construction of the first aspect of the present invention, an input shaft capable of inputting the power from the crankshaft and rotatably supported by a crankcase. The clutch operated by hydraulic pressure is mounted to one end portion of the input shaft projecting from the crankcase. Furthermore, a clutch control valve capable of controlling the hydraulic pressure provided to the clutch and constituting a portion of the second actuator is provided at a cover covering the clutch and coupled to the crankcase. According to such construction, the clutch and the clutch control valve are arranged at positions proximate to each other and operational response of the clutch by operation of the clutch control valve can be promoted.
A third aspect of the present invention includes, in addition to the construction of the second aspect of the present invention, a control unit for controlling a solenoid provided to the clutch control valve and controlling an electric motor constituting the first actuator. According to such a construction, the clutch control valve and the electric motor are electrically controlled and it is facilitated to operate the clutch in cooperation with shift operation of the gear transmission.
Furthermore, a fourth aspect of the present invention includes, in addition to the construction of the second or third aspects of the present invention, a torque converter covered by the cover is provided at one end portion of the crankshaft and a torque converter control valve for controlling hydraulic pressure provided to the torque converter is provided at the cover. According to such a construction, the clutch control valve and the torque converter control valve are provided at the cover, pressure leakage inspection at the two control valves can be carried out concentratedly on the side of the cover, which can contribute to promotion of productivity.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.